1. Field of the Invention
This invention relates generally to an instrument for diagnosing cancer, and, more particularly, to a hollow needle, including a fiber optic illuminator and a photodiode. for insertion into breast tissue to detect and analyze shifts in hemoglobin oxygenation.
2. Description of the Related Art
In a conventional procedure, a radiologist performs x-ray mammography. If an abnormal breast process recorded on the resulting mammograms is considered suspicious, a surgical biopsy can be ordered. Immediately prior to the biopsy, the radiologist takes several more views or projections of the breast during preoperative localization of the abnormality and marks the location of the suspicious abnormality by impaling the region with a thin, hooked guide wire. The patient is then taken to an operating room and a surgeon performing the biopsy follows the hooked wire guide to the precise location of the suspected abnormality. The most common form of biopsy involves surgically removing the suspected region. One of the less invasive forms of biopsy, stereotactic fine needle aspiration biopsy, aspirates a small amount of cells for cytologic analysis. The advantages of this technique are that it is minimally invasive, is accurate to less than 2 mm in lesion localization, has a sensitivity greater than 90%, and is less expensive than surgical biopsies. But since small (22 gauge) needles are used, cytology on the small amount of material removed is not easy. Far more accurate is large-core needle biopsy (using stereotactic positioning or ultrasound guidance), another alternative to surgical biopsy. Core biopsies remove a 1 mm.times.17 mm core of tissue (if a 14 gauge needle is used) for standard histological examination. However, benign histological diagnoses are difficult to make. In fact, for both fine needle aspiration biopsy and core biopsy, the techniques are only useful when they return a positive result for malignancy. In all other cases, the suspicious lesion must undergo incisional or excisional surgical biopsy.
False negatives in analyzing an x-ray mammogram occur when benign tumors or "normal" breast tissue with radiological densities similar to cancer completely or partially mask a malignant tumor which does not exhibit primary or secondary mammographic signs of carcinema. False positives are also problematic because they reduce the acceptability of mammography by the general public and lead to unnecessary biopsies.
Attempts have been made to use fibers to study biochemical and hemodynamic processes in tissues and to determine tissue type by using multiple fibers, one to deliver light and another to measure returning light. For example, see K. H. Frank et al., "The Erlangen micro-lightguide spectrophotometer EMPHO I," Phys. Med. Biol., vol. 34, No. 12, 1883-1900 (1989), Sung Chul Ji et al., "Micro-light guides: a new method for measuring tissue fluorescence and reflectance," American Journal of Physiology, vol. 236, C144-56 (March 1979); Kimizo One et al., "Fiber optic reflectance spectrophotometry system for in vive tissue diagnosis," Applied Optics, vol. 30, no. 1,98-105 (Jan. 1, 1991); and Irving J. Bigio et al., "The Optical Biopsy System," Los Alamos National Laboratory., Information Document (March 1992).
The optical absorption properties of malignant tissue differ in identifiable ways from those of normal and benign tissue, as described in F. A. Marks, "Optical determination of the hemoglobin oxygenation state of breast biopsies and human breast cancer xenographs in nude mice", SPIE Proceedings vol. 1641, 227-37 (January 1992). It would be useful to have an arrangement which measures optical absorption properties and has sufficient light detection capacity to perform a spectrum analysis in real time.